In this article, I would like to draw your attention to the question: what actually is ‘health’?
Is it when we have eradicated all diseases? Or when our bodies are resilient enough to fight any pathogens? Or is it when we establish a symbiotic relationship with our environment?
COVID-19 has taught us a painful lesson of the importance of sacrificing social contacts for the benefit of public health. Yet, the scope of health extends far beyond an individual, a community, a nation, or even the entire human species. Humans do not live on this planet alone, nor are there enough knowledge and resources in one sector to solve health issues across the globe; therefore, why should the definition of health, understanding of pathogens, and approach to diseases be limited to a single species?
Definition of One Health :
One Health is a collaborative, multisectoral, and trans-disciplinary approach – working at local, regional, national, and global levels – to achieve optimal health and well-being outcomes recognising the interconnections between people, animals, plants and their shared environment.
The bigger picture
Recognition of how human health is affected by animal and environmental factors has long been documented, such that wild birds are natural hosts for influenza viruses  and cholera is spread through contaminated water . Therefore, the conventional linear approach to treat diseases after emergence will not be sufficient to solve and prevent complex healthcare problems we face. For example, 75% of all emerging human infectious diseases are zoonotic (meaning they originated from other animals) , and climate change has been repeatedly proven to result in detrimental impacts on human health and livelihood, such as heat stress and food shortage [5, 6]. Eradicating rabies will not be possible without controlling dog population (i.e. through vaccinations), diagnosing respiratory diseases will not be complete without assessment of air quality. The knowledge and resources within the human healthcare sector simply aren’t adequate to define global healthcare challenges and fully understand aetiologies of complex diseases we face. Expertise from veterinarians, virologists, ecologists, conservationists, economists, social scientists, etc., will all provide beneficial, or even essential, perspectives and insights to tackle diseases. From outdoor activities to ozone layer depletion, from mad cow disease to human-animal interactions, we need to recognise that our physical and mental health are interdependent on the wellbeing of the animals, plants, and environment we cohabitate Earth with. Appreciating this multifaceted nature of ‘health’ is the first step to crossing the highly sectorized structure in healthcare and achieving more effective and sustainable disease control measures.
Besides reducing risks of infectious agents originating from animals and the environment, a One Health approach also broadens our perspectives to appreciate the abundant resources other living beings and nature may offer. Take penicillin as an example, this class of antibiotic has saved millions or even billions of lives since its discovery and was one of the most significant medical achievements of the 20th century. As novel as it could be in medical textbooks, this molecule has been synthesised by Penicillium fungi long before Fleming, which resulted from selective pressures between bacteria and fungi throughout the history of evolution. These symbiotic interactions and relationships between different lifeforms are the foundations for the ecosystem we see around us today. However, focusing on individual molecules or organisms may easily blind us to the holistic interconnections between different lifeforms. The rise of antibiotic resistance is a critical danger that shows how over-reliance on certain classes of drugs is leading to unprecedented risks on health. Using antibiotics doesn’t only kill off the ‘bad’ bacteria, but it also disrupts the intricate microbiome that contributes to more cells in human bodies than our own and drives the selection for resistant genes . Overuse of antibiotics both in medicine and veterinary medicine also lead to disastrous consequences to the environment around us, such as biodiversity loss. Nature is the greatest library of life and health. There is so much more to be discovered in order to diversify medical treatments and synchronise with nature.
‘Zoobiquity’ is a concept introduced by cardiologist Barbara Natterson-Horowitz that illustrates the benefits and importance of increasing collaboration between physicians and veterinarians. Although it seems apparent that there will be great opportunities for healthcare professionals of humans and other animals to work together, there seems to be more differentiations rather than interactions between the two fields. Currently there are little opportunities for medical and veterinary professionals to collaborate in clinical settings. Adopting a One Health approach in education, such as bringing medical and veterinary students together, and practice may help mitigate the current divided structures and maximise our potential to protect the health and welfare for all.
Despite the difficulties to implement this trans-disciplinary approach in the current established sectors and professions, One Health has been envisaged by certain institutional and global organisations (FAO, OIE, WHO, UNICEF, World Bank, etc) to address health risks at the human-animal-environment interface. This includes the establishment of The Manhattan Principles on “One World, One Health” (Figure 1 and 2) and the FAO/OIE/WHO Collaboration (Tripartite) to address global challenges such as antimicrobial resistance.
One Health is about establishing and strengthening linkages between different disciplines, people, animals, and the environment. This approach acknowledges the dependency we have on one another and the need to build a healthier relationship with livestock, wildlife, plants, air, water, and soil. The next time you buy a carton of eggs or drive on the M25, I encourage you to think about the veterinarians vaccinating hens against salmonella and environmental health scientists analysing pollutant concentrations.
As the Lion King sings:
“We are more than we are, we are one”.
 One Health Commission. What is One Health. One Health Commission website.
 CDC. Avian Influenza A Viruses. Centers for Disease Control and Prevention: Apr 19, 2017 [website].
 CDC. Cholera – Vibrio cholerae infection: General Information. Center for Disease Control and Prevention: Aug 5, 2020 [website].
 WHO. Neglected zoonotic diseases. World Health Organization [website].
 WHO. Heat and Health. World Health Organization: Jun 1, 2918 [website].
 EPA. Climate Impacts on Agriculture and Food Supply. United States Environmental Protection Agency [website].
 Langdon A., Crook N., & Dantas G. The effects of antibiotics on the microbiome throughout development and alternative approaches for therapeutic modulation. Genome Medicine 8(39): Apr 13, 2016.